Recovery partition fills up half of the disk, cannot resize

My suggestion

Don't try to resize from the Recovery partition. Boot into the normal partition and resize from there.

Background

diskutil list is misleading you. It is not the position of the recovery partition which is your problem.

I had a very similar setup, and here is the output of diskutil list for me:

  #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk0
   1:                        EFI                         209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            423.6 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:                  Apple_HFS Temp Partition Test ... 74.8 GB    disk0s4
   5:                 Apple_Boot Recovery HD             792.2 MB   disk0s5

Partitions 4 and 5 had a dev version of Lion on them. I have just used Disk utility to delete partitions 4 and 5 and resize partition 2 to fill the space.

This worked - Disk Utility resized the main drive with no problem. So what have I done which is different to you? Well, I resized the main partition from booting into the main partition not the Recovery Partiion. You can resize a partition that you have booted from in Disk Utility.

It makes sense that the recovery partition would "get in the way" if you have booted from it, so I suspect that above suggestion might work for you.

Although I don't know what specific property of HFS+ allows a user to modify the current system partition while in use; my expectation would be that operations to blocks of storage that the filesystem is not currently utilizing are allowed.

Now if you tried to shrink the system partition below the current size of your system installation (the blue shaded area) disk utility would present an error.

EDIT

Just wanted to add some additional information that I came across. If you refer to the diskutil(8) man page under resizeVolume it states:

Non-destructively resize a volume. You may increase or decrease its size.

A size of limits will print the range of valid values for the target partition, taking into account current file system and partition map conditions such as files in use and other (immovable) partitions following the target.

This seems to confirm my thinking above.